Britain, France, Ireland and Spain are to launch a bid to extend their territorial waters at a UN conference on ocean rights.
In a joint submission to the UN Commission on the Limits of the Continental Shelf, the four states have applied to extend their territorial waters in the Bay of Biscay and the Celtic Sea to beyond the current legal limit of 200 nautical miles.
A French scientist say France will also file other requests concerning zones surrounding its overseas territories of the Kerguelen Islands in the Indian Ocean, New Caledonia in the Pacific and French Guiana in Latin America.
France, whose exclusive economic zone currently covers 10.2 million square kilometres, hopes to gain an extra one million square kilometres.
Countries would get exclusive rights to exploit hydrocarbons, minerals, living species on the ocean floor and bacteria for use in biotechnology.